Tremor

Parkinsonian, Intention, Ataxic, Cerebellar, Postural, Action

What is tremor?

Tremors are involuntary, usually rhythmic muscle movements. These movements occur in a to-and-fro fashion (oscillations) and affect one or more parts of the body. Tremors most often affect a person's hands, but may also affect the arms, head, face, vocal cords, trunk and legs.

Most people who experience tremors are otherwise healthy. Such tremors are known as physiologic tremors, and they often can be caused by engaging in demanding activity, becoming physically exhausted or experiencing extreme emotions such as excitement, fear or stress. However, in some cases, people may experience tremors as part of certain neurological conditions, such as multiple sclerosis, neurodegenerative disorders, stroke and traumatic brain injury. Other potential sources of tremors include the presence of other diseases, use of certain medications, alcohol abuse or withdrawal, poisoning, an overactive thyroid and liver failure.

People sometimes confuse a type of tremor known as essential tremor with the illness Parkinson's disease. Essential tremor is one of the most common types of movement disorders. It may cause difficulties in performing certain tasks, such as activities that require fine motor skills. However, it is not linked to any other disease and rarely leads to serious medical complications. In contrast, Parkinson's disease is a chronic, progressive disease that may eventually damage a patient's ability to perform basic tasks, including talking and walking.

In some cases, tremors may occur intermittently. Some people may find that certain activities trigger their tremors. Stress or other strong emotions, physical exhaustion, and certain postures and movements are known to cause tremors. Other patients may find that their tremor is only temporary and eventually disappears over time.

Tremors do not usually pose serious health risks. However, they may make it difficult to perform certain daily activities. For example, people with hand tremors may have difficulty writing, dressing (e.g., shaving, buttoning a shirt) or eating (e.g., holding a glass or eating utensils).

Types and differences of tremors

Tremor types are often classified according to when they occur or what triggers the tremors, including:

Resting or static tremors

These occur when the muscles are relaxed and the limbs are supported against gravity. It is often seen in patients with Parkinson’s disease.

Postural tremors

Occur when a person holds a certain position against gravity without support for a period of time. One example is holding the arms outstretched.

Isometric tremors

Occur during muscle contraction that is not accompanied by movement. For example, tremors that occur when making a fist or pushing against a wall.

Action tremors

Tremors that occur during intentional movement, such as touching a finger to one’s nose, writing or speaking. These tremors disappear when the patient is at rest. They may also be referred to as kinetic tremors, intention tremors or task-specific tremors. Isometric tremors and postural tremors may be considered types of action tremors.

Physiologic tremors

Certain events can trigger tremors, including strong emotions (e.g., anxiety, fear, anger) and physical exhaustion. Other bodily conditions can cause this type of tremor, including low blood sugar (hypoglycemia), excessive production of thyroid hormone (hyperthyroidism), heavy metal poisoning, use of stimulants, alcohol abuse and withdrawal. Every person experiences physiologic tremors upon occasion. However, they are rarely visible to the naked eye. If the tremor becomes more significant, it may be a classified as an enhanced physiologic tremor, which is more likely to be visible.

Tremor types may also be categorized by their clinical features or cause, including:

Essential tremors

The most common neurologic tremor, it often affects the hands and head, but may affect other body parts as well (e.g., arms, vocal cords, trunk, legs). It occurs in conjunction with purposeful movement (e.g., holding a glass, writing, speaking) and typically does not occur during rest or sleep. In some people, the tremor is mild, asymmetric and does not worsen. Others may experience a progression that eventually causes the tremor to affect both sides of the body.

Certain factors seem to trigger these tremors, including heightened emotions or stress, fever, physical exhaustion and low blood sugar. This type of tremor usually develops in middle age or later in life, although it is not associated with any type of disease or medical condition. There is often a family history of essential tremor, which is estimated to affect as many as 10 million Americans, according to the International Essential Tremor Foundation.

Parkinsonian tremors

Often precede the development of Parkinson’s disease and may start on one side of the body before affecting the other side as well. It generally occurs after age 60 and may affect the hands (in which it appears as a “pill rolling” movement), chin, lips, trunk and legs. Stress and high emotions may bring on symptoms. This type of tremor may also be associated with other medical conditions.

Dystonic tremors

Occur in people with dystonia, a movement disorder in which involuntary muscle contractions cause twisting and repetitive motions and other abnormal postures or positions that cause pain to the patient. Tremors can occur with no discernible pattern and often can be relieved by complete rest. In some cases, the patient is able to control tremor intensity merely by touching the affected body part.

Cerebellar tremors

Tremors of the extremities that occur when a person engages in a purposeful movement, such as touching the nose with the end of a finger. It results from damage to the cerebellum in the brain following stroke, tumor, disease (e.g., multiple sclerosis) or an inherited condition such as a neuro-degenerative disorder. Use of certain medications and alcohol abuse can also cause this type of tremor. Tremors tend to worsen with activity or while maintaining certain postures.

Psychogenic tremors (also called hysterical tremors)

Often result due to psychological disorders such as conversion disorder (loss of motor or sensory function without a physiological basis) or other mental illnesses. Symptoms can occur during rest or movement. It often comes and goes suddenly, with stress tending to bring on episodes. Tremors are likely to disappear when the patient is otherwise engaged or distracted.

Orthostatic tremors

Often occur in the legs and trunk while standing. Patients may feel cramps in the thighs and legs and are often unable to stand in one spot without shaking uncontrollably. This shaking stops when the patient sits or is lifted off the ground.

Physical exam: In addition to different types of tremors, rigidity, mask-like face, and other clinical signs can be detected.

Tests: Electromyographic (EMG) studies are indicated.

How is tremor treated?

To determine the underlying cause of tremors, a physician will perform a complete physical examination and obtain a thorough medical history. Various tests may be performed to look for sensory loss, decreased reflexes, and weakness or muscle atrophy. Blood tests, urine tests, imaging tests and a neurological examination may also be performed.

In some cases, tremors are so mild that they do not affect a person’s daily activities and may not require treatment. In other cases, tremors may be more severe. In such situations, treatment usually focuses on trying to manage the tremors as much as possible.

Various medications, including anticholinergic medications, are available to treat several types of tremors. In addition, patients with some types of tremors can benefit from treatment with botulinum toxin.

In some cases, the most effective way to treat a tremor is to address the underlying condition that causes the tremor. For example, psychogenic tremors can often be relieved by successfully treating a patient’s underlying psychological disorder.

Avoiding certain causes or triggers may also help reduce the incidence of tremors. For instance, reducing stress can help curb tremors in some patients. Others find that their tremors become less frequent and/or less severe when they decrease consumption of caffeine or other stimulants. If tremors are caused by certain medications, discontinuing use or switching to another type of medication may relieve a patient’s tremors. However, patients are advised not to discontinue their current medications without first consulting their physician.

Physical therapy can help patients improve coordination and muscle control, which can reduce the incidence of tremors.

Severe tremors may require surgery for optimal control. Thalamotomy is a procedure that creates lesions in an area of the brain called the thalamus. It is often effective in reducing essential tremors, cerebellar tremors or Parkinsonian tremors. Deep brain stimulation uses electrodes implanted in the brain to send high-frequency electrical signals to the thalamus to disable tremors. This procedure is often used to treat Parkinsonian tremors and essential tremors.

Some patients may find that their tremors subside when they drink alcohol. However, physicians generally do not recommend this as a treatment for tremors. In fact, people who regularly consume large quantities of alcohol can experience withdrawal symptoms that include tremors.

Medications

What might complicate it?

Anxiety, emotional stress, alcohol, and some medications can aggravate the tremor. Other complications depend on the underlying disorder.

Predicted outcome

The tremor can seriously affect the individual's quality of life. It is usually a chronic and progressive disorder, and involvement of additional body parts may be expected. On the other hand, enhancement of physiologic tremors that occur in various metabolic and toxic states is temporary.